System, control method and apparatus for chemical mechanical polishing

ABSTRACT

Disclosed are a chemical mechanical polishing apparatus, a control method for the chemical mechanical polishing apparatus and a chemical mechanical polishing system. In one embodiment, the chemical mechanical polishing apparatus includes a polishing pad, a sensor, a polishing head and a conditioner. The sensor is configured to obtain surface roughness of the polishing pad. The polishing head is located above the polishing pad and configured to polish a wafer which is push against the polishing pad. The conditioner is located on the polishing pad and configured to recondition the polishing pad, wherein the conditioner is operated according to at least one polishing condition, and the polishing condition is tuned according to the surface roughness of the polishing pad.

BACKGROUND

During semiconductor fabrication process, a substrate (e.g.,semiconductor wafer) may be polished or planarized one or more times toremove a portion on a top surface of the wafer. A typical polishingprocess is a chemical mechanical polishing (CMP), where the wafer ispolished by being placed on polishing head and pressed facedown onto thepolishing pad. During the polishing process, the characteristic of thepolishing pad may be changed (e.g., polishing pad may be worn out),thereby reducing the polishing rate and the quality of the polishedwafer. Thus, pad conditioning is performed by a conditioner torecondition the surface of the polishing pad. However, the existingapproaches do not provide an effective way to monitor conditions orprofile of the polishing pad and make appropriate adjustments for theCMP apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 and FIG. 2 schematically illustrate a top view and a side view ofa chemical-mechanical polishing (CMP) system in accordance with someembodiments of the present disclosure.

FIG. 3 schematically illustrates a block diagram of a closed loopcontrol system for CMP process stability in accordance with someembodiments of the present disclosure.

FIG. 4A through FIG. 9 schematically illustrate various flowcharts ofcontrol methods for chemical mechanical polishing apparatus inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one component or feature's relationship toanother component(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

Chemical-mechanical polishing (CMP) is one of the commonly usedpolishing solutions. Ideally, a wafer should be polished homogeneouslyand uniformly across the entire wafer. The removal rate should beidentical on every measurement spot within a wafer. Unfortunately, inreality, the removal rate has regional variation, which results in athickness variation within wafer (WiW), wafer to wafer (WtW) or lot tolot (LtL). The removal rate of the CMP process has a high correlationwith surface roughness (e.g., Ra, Rpk, or Rvk) of a polishing pad. “Ra”stands for average, or arithmetic average of profile height deviationsfrom the mean line. “Rpk” stands for average of peak height above themean line. “Rvk” stands for average of valley depth below the mean line.If the surface roughness of the polishing pad is analyzed after the endof pad life time, the surface roughness of the polishing pad cannot beobtained in time when the removal rate and WiW/WtW/LtL thickness vary orcontinuously increase or decrease during polishing. In addition,un-optimized conditioning recipe can also lead to increasing ordecreasing removal rate at some positions/regions of the polishing padover the period of pad life, which may increase the out of control rateand rework rate of the volume production. In order to acquire a goodconditioning recipe, lots of wafers (over 600 pcs) would be used fortuning (so-called marathon experiment), which could also take a largeamount of time (normally one week) and resources(wafer/slurry/chemical).

The present disclosure is related to a chemical mechanical polishingapparatus, a control method for the chemical mechanical polishingapparatus and a chemical mechanical polishing system to form a planartop surface of the wafer (or other object). In some embodiments, a padconditioning process is performed prior to or synchronously with thechemical mechanical polishing process to control surface roughness(e.g., at least one of Ra, Rpk and Rvk) of the polishing pad so thatremoval rate within the polishing pad is uniform, which helps improveWiW, WtW or LtL uniformity of the chemical mechanical polishing process.

FIG. 1 and FIG. 2 schematically illustrate a top view and a side view ofa chemical-mechanical polishing system in accordance with someembodiments of the present disclosure. FIG. 3 schematically illustratesa block diagram of a closed loop control system for CMP processstability in accordance with some embodiments of the present disclosure.FIG. 4 through FIG. 9 schematically illustrate various flowcharts ofcontrol methods for chemical mechanical polishing apparatus inaccordance with some embodiments of the present disclosure.

Referring to FIG. 1 and FIG. 2 , a chemical-mechanical polishing system1 in accordance with some embodiments of the present disclosure isprovided. The chemical-mechanical polishing system 1 includes a chemicalmechanical polishing apparatus 10 and a controller CT, but the presentdisclosure is not limited thereto. The chemical-mechanical polishingsystem 1 may further include other elements or devices according todifferent requirements. For example, although not shown in the figures,the chemical-mechanical polishing system 1 may further include a memoryconnected to the controller CT, or other elements or devices.

The chemical mechanical polishing apparatus 10 in accordance with someembodiments of the present disclosure includes a polishing pad P, asensor MS, a polishing head H and a conditioner CD, but the presentdisclosure is not limited thereto. The chemical mechanical polishingapparatus 10 may further include other elements according to differentrequirements. For example, the chemical mechanical polishing apparatus10 may further include a platen PL, a robotic arm R and a slurrydispenser SD, but the present disclosure is not limited thereto.

The polishing pad P is disposed on or attached to the platen PL. Whenthe platen PL rotates, the polishing pad P rotates accordingly. Thepolishing pad P may include a plurality of grooves (not shown) formedrandomly or in any specific pattern as long as the grooves are able toprovide the desired functions. For example, the patterns of the groovesmay include concentric circular pattern, radial pattern, Cartesian gridpattern, spiral pattern, rotated Cartesian grid pattern, and anycombination thereof.

The sensor MS is configured to obtain surface roughness of the polishingpad P. In some embodiments, the sensor MS is located above the polishingpad P, and the sensor MS obtains the surface roughness of the polishingpad P in a non-contact manner. In this way, damage to the polishing padP caused by surface roughness measurement can be reduced. In someembodiments, the sensor MS is configured to capture images of thepolishing pad P to obtain surface roughness of the polishing pad P. Insome embodiments, the sensor MS includes confocal microscopy, athree-dimensional image sensor or other devices that are capable ofobtaining three-dimensional images of the polishing pad P. Thethree-dimensional images of the polishing pad P can be used to confirmsurface morphology of the polishing pad P, and the surface roughnessinformation of the polishing pad P can be calculated or obtained fromthe surface morphology of the polishing pad P.

A field of view (FOV, i.e., the maximum region of the polishing pad Pthat the sensor MS can image) of the sensor MS may be larger than, equalto or smaller than an area of the polishing pad P. When the field ofview of the sensor MS is smaller than the area of the polishing pad P,the sensor MS is unable to capture the image of the entire polishing padP at one time (or with one shot). In the embodiments in which the fieldof view of the sensor MS is smaller than the area of the polishing padP, the robot arm R is configured to move the sensor MS so that thesensor MS can capture images that cover the entire polishing pad P. Forexample, the robotic arm R is configured to move the sensor MS between acenter and an edge of the polishing pad P (as indicated by the doublearrow inside the outline of the polishing pad P in FIG. 1 ) so that thesensor MS is able to capture images correspond to regions between thecenter and the edge of the polishing pad P, and thus the surfaceroughness of the entire polishing pad P (from the center to the edge)can be obtained or calculated from the three-dimensional images obtainedby the sensor MS.

In some embodiments, the sensor MS is fixed to an end portion of therobotic arm R or hold by the end portion of the robotic arm R, so thatwhen the end portion of the robotic arm R moves between the center andthe edge of the polishing pad P, the sensor MS moves with the robot armR between the center and the edge of the polishing pad P. It should benoted that the relative position or connection manner of the robotic armR and the sensor MS shown in FIG. 1 and FIG. 2 is for illustrationpurposes and the present disclosure is not limited thereto.

The polishing head H is located above the polishing pad P and configuredto polish a wafer W which is push against the polishing pad P.Specifically, the polishing head H may provide a controllable load tothe wafer W to push the wafer W against the polishing pad P. Duringpolishing process, the polishing head H may rotate with a specific oradjustable downward force to polish the wafer W.

In some embodiments, the polishing head H includes a carrier head CH, amembrane MB and a retaining ring RR, but the present disclosure is notlimited thereto. The membrane MB is located between the carrier head CHand the wafer W. A space (or a cavity or a chamber) between the carrierhead CH and the membrane MB can be sealed. Sealing the cavity betweenthe membrane MB and the carrier head CH allows the cavity to bepositively or negatively pressurized as required.

The membrane MB may be flexible and includes an inner surface that formsthe boundary of a pressurizable chamber (not labeled) and an outersurface that forms a mounting surface to receive a backside of the waferW and to press a frontside of the wafer W against the polishing pad P.During polishing, the chamber is pressurized to cause the membrane MB toexpand outwardly and apply the load to the wafer W, which presses thewafer W against the polishing pad P. After polishing, the wafer W ischucked to the outer surface, lifted off the polishing pad P, and movedto another location, such as a transfer station or another polishingpad.

The retaining ring RR surrounds the membrane MB, and the wafer W can beheld by the retaining ring RR. Specifically, the retaining ring RR mayhave an inner surface and a lower surface, wherein the inner surface ofthe retaining ring RR can be configured to circumferentially surroundthe edge of the wafer W to retain the wafer W during polishing, and thelower surface of the retaining ring RR can be brought into contact withthe polishing pad P.

The slurry dispenser SD is configured to supply polishing slurry S tothe surface of the polishing pad P during polishing process. Thepolishing slurry S may include at least one chemically reactive agentand abrasive particles, but the present disclosure is not limitedthereto. In some embodiments, the slurry dispenser SD may be furtherconfigured to control a flow rate of the polishing slurry S. In someembodiments, the flow rate of the polishing slurry S may be tuned duringthe polishing process according to the surface roughness of thepolishing pad P.

The conditioner CD is located on the polishing pad P and configured torecondition the polishing pad P so as to recover the characteristics(e.g., surface roughness) of the polishing pad P. In some embodiments,the conditioner CD may be made from metal which is embedded with diamondparticles, but the present disclosure is not limited thereto. In someembodiments, the conditioner CD is operated according to at least onepolishing condition, and the polishing condition is tuned according tothe surface roughness of the polishing pad P. In some embodiments, theat least one polishing condition includes at least one of a rotationalspeed of the conditioner CD, a downward force of the conditioner CD thatpushes the wafer W against the polishing pad P and a polishing time ofthe conditioner CD, but the present disclosure is not limited thereto.For example, the at least one polishing condition may include at leastone of a sweep range and a sweep frequency of the conditioner CD, butthe present disclosure is also not limited thereto.

The conditioner CD generally rotates and moves between the center andthe edge of the polishing pad P as indicated by the double arrow insidethe outline of the polishing pad P in FIG. 1 . In some embodiments, therobotic arm R is further configured to move the conditioner CD betweenthe center and the edge of the polishing pad P so that the conditionerCD is able to polish the polishing pad P from the center to the edge ofthe polishing pad P. For example, the conditioner CD may be fixed to therobotic arm R at a position near the sensor MS so that the conditionerCD may be moved synchronously with the sensor MS, and that the sensor MSis able to capture images of the polishing pad P near the conditionerCD, and thus the surface roughness of the polishing pad P near theconditioner CD can be obtained. In other embodiments, although notshown, the conditioner CD and the sensor MS may be fixed to differentrobotic arms, and the conditioner CD may be moved synchronously orasynchronously with the sensor MS.

In some embodiments, the conditioner CD and the sensor MS may be movedin parallel on the polishing pad P, and the sensor MS can capture imagesof the polishing pad P that is reconditioned by the conditioner CD, butthe present disclosure is also not limited thereto. In otherembodiments, although not shown, the sensor MS may be positionedupstream of the conditioner CD, and the sensor MS can capture images ofthe polishing pad P that is to be reconditioned by the conditioner CD;or the sensor MS may be positioned downstream of the conditioner CD, andthe sensor MS can capture images of the polishing pad P alreadyreconditioned by the conditioner CD; or two sensors MS may be providedupstream and downstream of the conditioner CD to capture images of thepolishing pad P to be reconditioned and already reconditioned by theconditioner CD.

Once the surface roughness of the polishing pad P is obtained by thesensor MS, the at least one polishing condition (parameters) of theconditioner CD may be tuned according to the obtained/calculated surfaceroughness. In some embodiments, at least one of the rotational speed ofthe conditioner CD, the downward force of the conditioner CD, thepolishing time of the conditioner CD, the sweep range of the conditionerCD and the sweep frequency of the conditioner CD are tuned according tothe surface roughness of the polishing pad P. However, the presentdisclosure is not limited thereto and any other polishing conditions (orparameters) of the conditioner CD may be tuned according to the surfaceroughness of the polishing pad P.

The controller CT is coupled to the chemical mechanical polishingapparatus 10, and is configured to tune at least one polishing conditionaccording to the surface roughness of the polishing pad P and controlthe conditioner CD according to the at least one polishing condition.For example, the controller CT is coupled to the sensor MS to receivedata or obtained results from the sensor MS, and the controller CT iscoupled to the conditioner CD to control the conditioner CD according tothe at least one polishing condition.

Referring to FIG. 3 , a closed loop control system for a padconditioning process in accordance with some embodiments of the presentdisclosure is provided. The closed loop control system for a padconditioning process may include a filter F, the controller CT, theconditioner CD and the sensor MS, but the present disclosure is also notlimited thereto.

A pad conditioning process may be activated when a start signal is inputto the filter F. The filter F is configured to filter noises in thestart signal or any other signal to be input to the controller CT. Insome embodiments, the filter F can be hardware or software (e.g.,programmable code or algorithm) stored in the controller CT. In otherembodiments, the filter F may be hardware provided in a device (notshown) other than the controller CT or software stored in the cloud.

The controller CT receives the signal filtered by the filter F. Thecontroller CT may be a micro-IC, a computing device or any other devicethat is capable of receiving, processing and transmitting signal(s),performing calculation and/or determination step(s) and controlling theconditioner CD or any other device based on the signal(s). In someembodiments, the surface roughness of the polishing pad P is calculatedby the controller CT based on the signals produced from the sensor MSand filtered by the filter F; alternatively, the surface roughness ofthe polishing pad P may be calculated by the processor stored in thesensor MS or in other device or by the software stored in the cloud. Thecontroller CT determines whether at least one of the polishingconditions (e.g., the rotational speed of the conditioner CD, thedownward force of the conditioner CD, the polishing time of theconditioner CD, the sweep range of the conditioner CD and the sweepfrequency of the conditioner CD) should be tuned according to theobtained surface roughness and instruct the conditioner CD to operateaccordingly.

Take FIG. 2 as an example, the wafer W is positioned between the centerand the edge of the polishing pad P, wherein the peripheral region ofthe wafer W corresponds to the center and edge regions of the polishingpad P, and the central region of the wafer W corresponds to anintermediate region of the polishing pad P between the center and theedge of the polishing pad P. If the surface roughness of the center andedge regions of the polishing pad P is lower than the surface roughnessof the intermediate region of the polishing pad P, the removal rate inthe central region of the wafer W will be greater than the removal ratein the peripheral region of the wafer W. Namely, the central region ofthe wafer W will be removed faster than the peripheral region of thewafer W. When the controller CT confirms the existence of surfaceroughness variation of the polishing pad P and the surface roughnessvariation is higher than an acceptable value, the controller CTdetermines that at least one of the polishing conditions should beadjusted and instructs the conditioner CD to act accordingly.

Since the above listed polishing conditions (parameters) of theconditioner CD is correlated with the removal rate, the surfaceroughness variation of the polishing pad P can be reduced by tuning atleast one of the polishing conditions, thereby making the removal rateof the entire surface of the wafer W more uniform. For example, therotational speed, the downward force and the polishing time of theconditioner CD are positively correlated with the removal rate, namely,the higher the rotational speed/the downward force/the polishing time,the higher the removal rate. Therefore, at least one of the rotationalspeed, the downward force and the polishing time of the conditioner CDmay be increased when the conditioner CD reaches the center or the edgeregion of the polishing pad P, and at least one of the rotational speed,the downward force and the polishing time of the conditioner CD may bedecreased or remain the same when the conditioner CD reaches theintermediate region of the polishing pad P, so that the reconditionedpolishing pad P has a more uniform overall surface roughness.

Referring back to FIG. 3 , the sensor MS may capture images of thereconditioned or to-be-reconditioned polishing pad P and producecorresponding signals to the filter F. For example, the sensor MSincludes confocal microscopy or a three-dimensional image sensor, butthe present disclosure is not limited thereto. In some embodiments, afield of view of the sensor MS is smaller than an area of the polishingpad P, and capturing the images of the polishing pad P includes movingthe sensor MS between a center and an edge of the polishing pad P sothat the sensor MS is able to capture images correspond to regionsbetween the center and the edge of the polishing pad P. The signals fromthe sensor MS are filtered by the filter F and then transmitted to thecontroller CT. The controller CT determines whether at least one of thepolishing conditions should be tuned according to the obtained surfaceroughness and instruct the conditioner CD to operate accordingly.

By continuously and timely tuning at least one of the polishingconditions of the conditioner CD, the uniformity of the surfaceroughness of the polishing pad P can be improved, thereby improving WiW,WtW or LtL uniformity of the chemical mechanical polishing process.Since the surface roughness variation can be reduced and stability ofthe polished thickness can be controlled, higher yield can be achievedand wafer acceptance test (WAT) performance can be boosted. In addition,the pad life time may be extended, the time, cost and resources foracquiring a good conditioning recipe may be reduced.

Referring to FIG. 4A and FIG. 4B, a control method for a chemicalmechanical polishing apparatus (e.g., the chemical mechanical polishingapparatus in FIG. 1 and FIG. 2 ) in accordance with some embodiments ofthe present disclosure is provided. The control method may include a padconditioning process (step S1), a CMP process (step S2) and a cleaningprocess (step S3) performed in sequence, but the present disclosure isnot limited thereto.

In some embodiments, the pad conditioning process (step S1) may includethe following steps: capturing, by the sensor, images of the polishingpad to obtain surface roughness of the polishing pad (step S10); tuningat least one polishing condition according to the surface roughness ofthe polishing pad (step S11); and reconditioning, by the conditioner,the polishing pad according to the at least one polishing condition(step S12), as shown in FIG. 4B, but the present disclosure is notlimited thereto.

In step S10, the sensor may include confocal microscopy, athree-dimensional image sensor or other devices that are capable ofobtaining three-dimensional images of the polishing pad. When the fieldof view of the sensor MS is smaller than the area of the polishing padP, capturing the images of the polishing pad includes moving the sensorbetween the center and the edge of the polishing pad so that the sensoris able to capture images correspond to regions between the center andthe edge of the polishing pad, thereby the surface roughness of variousregions of the polishing pad can be obtained.

In step S11, the at least one polishing condition of the conditioner maybe tuned by the controller according to the surface roughness of thepolishing pad, and the controller instructs the conditioner to operateaccording to the at least one of the polishing conditions. For example,when the existence of surface roughness variation of the polishing padis confirmed by the controller and the surface roughness variation isdetermined to be higher than an acceptable value by the controller, thecontroller determines that at least one of the polishing conditionsshould be adjusted and instructs the conditioner to act accordingly. Forexample, at least one of the rotational speed of the conditioner CD, thedownward force of the conditioner CD, the polishing time of theconditioner CD, the sweep range of the conditioner CD and the sweepfrequency of the conditioner CD may be tuned according to the obtainedsurface roughness.

In step S12, reconditioning the polishing pad includes moving theconditioner between the center and the edge of the polishing pad so thatthe conditioner is able to polish the polishing pad from the center tothe edge of the polishing pad. In some embodiments, the sensor and theconditioner are moved synchronously, but the present disclosure is notlimited thereto.

In some embodiments, the step of reconditioning the polishing pad isperformed prior to the step of polishing the wafer (step S2). In someembodiments, the CMP process (step S2) may include polishing a waferwhich is push against the polishing pad by the polishing head. Asdescribed above, the polishing head may rotate with a specific oradjustable downward force to polish the wafer during the polishingprocess. For other related descriptions, please refer to the above, andwill not be repeated here.

In some embodiments, the cleaning process (step S3) may include apost-CMP cleaning process to remove the residual slurry particles,organic residues, foreign materials, metallic impurities, etc., from thewafer surfaces. Various kinds of cleaning solutions, such as SC-1, SC-2,SPM and/or DHF, may be adopted to meet the requirements for the level ofacceptable defects.

Referring to FIG. 5 , a control method for a chemical mechanicalpolishing apparatus (e.g., the chemical mechanical polishing apparatusin FIG. 1 and FIG. 2 ) in accordance with some embodiments of thepresent disclosure is provided. The main difference between the controlmethod in FIG. 5 and the control method in FIG. 4A is that the controlmethod in FIG. 5 further includes another pad reconditioning process(step S1) performed after the step S3. In other words, the step ofreconditioning the polishing pad (step S1) is performed again after thestep of polishing the wafer (step S2), or, as shown in FIG. 5 , afterthe cleaning process (step S3). For details of the two steps S1, step S2and step S3, please refer to the related description of FIG. 4B, whichwill not be repeated here.

By performing the step of reconditioning the polishing pad (step S1)after the cleaning process (step S3), the polishing pad can have auniform surface roughness before the next CMP process.

Referring to FIG. 6 , a control method for a chemical mechanicalpolishing apparatus (e.g., the chemical mechanical polishing apparatusin FIG. 1 and FIG. 2 ) in accordance with some embodiments of thepresent disclosure is provided. The control method in FIG. 6 may includea pad conditioning process and a CMP process performed synchronously(step S1′) and a cleaning process (step S3), wherein step S1′ and stepS3 are performed in sequence, hut the present disclosure is not limitedthereto.

In step S1′, the step of reconditioning the polishing pad is performedsynchronously with the step of polishing the wafer. Namely, during thewafer polishing process, the pad conditioning process described in FIG.3 and FIG. 4B is performed at the same time. During the wafer polishingprocess, by continuously and timely obtaining the surface roughnessinformation and adjusting at least one polishing condition of theconditioner accordingly, the steps required for the control method canbe simplified and the uniformity of the removal rate can be effectivelycontrolled, thereby helping to improve the WiW thickness uniformity.

Referring to FIG. 7 , a control method for a chemical mechanicalpolishing apparatus (e.g., the chemical mechanical polishing apparatusin FIG. 1 and FIG. 2 ) in accordance with some embodiments of thepresent disclosure is provided. The main difference between the controlmethod in FIG. 7 and the control method in FIG. 6 is that the controlmethod in FIG. 7 further includes a pad reconditioning process (step S1)performed after the step S3. In other words, the step of reconditioningthe polishing pad (step S1) is performed again after the step ofpolishing the wafer (e.g., step S1′), or, as shown in FIG. 7 , after thecleaning process (step S3). For details of the step S1′, step S3 andstep S1, please refer to the related description above, which will notbe repeated here.

Referring to FIG. 8 , a control method for a chemical mechanicalpolishing apparatus (e.g., the chemical mechanical polishing apparatusin FIG. 1 and FIG. 2 ) in accordance with some embodiments of thepresent disclosure is provided. The main difference between the controlmethod in FIG. 8 and the control method in FIG. 7 is that the step ofreconditioning the polishing pad (step S1) is performed prior to thestep of polishing the wafer (e.g., step S1′), and the step ofreconditioning the polishing pad is performed again synchronously withthe step of polishing the wafer (e.g., step S1′).

By performing the step of reconditioning the polishing pad (step S1)before the step of polishing the wafer (e.g., step S1′), the polishingpad can have a uniform surface roughness before the CMP process.

Referring to FIG. 9 , a control method for a chemical mechanicalpolishing apparatus (e.g., the chemical mechanical polishing apparatusin FIG. 1 and FIG. 2 ) in accordance with some embodiments of thepresent disclosure is provided. The main difference between the controlmethod in FIG. 9 and the control method in FIG. 8 is that the controlmethod in FIG. 9 further includes a pad reconditioning process (step S1)performed after the step S3. In other words, the step of reconditioningthe polishing pad (step S1) is performed for the third time after thestep of polishing the wafer (e.g., step S1′), or, as shown in FIG. 9 ,after the cleaning process (step S3). For details of the step S1′, stepS3 and the two steps S1, please refer to the related description above,which will not be repeated here.

Based on the above discussions, it can be seen that the presentdisclosure offers various advantages. It is understood, however, thatnot all advantages are necessarily discussed herein, and otherembodiments may offer different advantages, and that no particularadvantage is required for all embodiments.

In accordance with some embodiments of the present disclosure, achemical mechanical polishing apparatus includes a polishing pad, asensor, a polishing head and a conditioner. The sensor is configured toobtain surface roughness of the polishing pad. The polishing head islocated above the polishing pad and configured to polish a wafer whichis push against the polishing pad. The conditioner is located on thepolishing pad and configured to recondition the polishing pad, whereinthe conditioner is operated according to at least one polishingcondition, and the polishing condition is tuned according to the surfaceroughness of the polishing pad. In some embodiments, the sensor isconfigured to capture images of the polishing pad to obtain surfaceroughness of the polishing pad. In some embodiments, the sensor includesconfocal microscopy or a three-dimensional image sensor. In someembodiments, a field of view of the sensor is smaller than an area ofthe polishing pad, and the chemical mechanical polishing apparatusfurther includes a robotic arm configured to move the sensor between acenter and an edge of the polishing pad so that the sensor is able tocapture images correspond to regions between the center and the edge ofthe polishing pad. In some embodiments, the robotic arm is furtherconfigured to move the conditioner between the center and the edge ofthe polishing pad so that the conditioner is able to polish thepolishing pad from the center to the edge of the polishing pad. In someembodiments, the at least one polishing condition includes at least oneof a rotational speed of the conditioner, a downward force of theconditioner that pushes the wafer against the polishing pad and apolishing time of the conditioner.

In accordance with some embodiments of the present disclosure, a controlmethod for a chemical mechanical polishing apparatus having a polishingpad, a sensor, a polishing head and a conditioner includes the followingsteps: capturing, by the sensor, images of the polishing pad to obtainsurface roughness of the polishing pad; tuning at least one polishingcondition according to the surface roughness of the polishing pad;polishing a wafer which is push against the polishing pad by thepolishing head; and reconditioning, by the conditioner, the polishingpad according to the at least one polishing condition. In someembodiments, the sensor includes confocal microscopy or athree-dimensional image sensor. In some embodiments, a field of view ofthe sensor is smaller than an area of the polishing pad, and capturingthe images of the polishing pad includes moving the sensor between acenter and an edge of the polishing pad so that the sensor is able tocapture images correspond to regions between the center and the edge ofthe polishing pad. In some embodiments, reconditioning the polishing padincludes moving the conditioner between the center and the edge of thepolishing pad so that the conditioner is able to polish the polishingpad from the center to the edge of the polishing pad. In someembodiments, the sensor and the conditioner are moved synchronously. Insome embodiments, the at least one polishing condition includes at leastone of a rotational speed of the conditioner, a downward force of theconditioner that pushes the wafer against the polishing pad and apolishing time of the conditioner. In some embodiments, the step ofreconditioning the polishing pad is performed prior to the step ofpolishing the wafer. In some embodiments, the step of reconditioning thepolishing pad is performed again after the step of polishing the wafer.In some embodiments, the step of reconditioning the polishing pad isperformed again synchronously with the step of polishing the wafer. Insome embodiments, the step of reconditioning the polishing pad isperformed for the third time after the step of polishing the wafer. Insome embodiments, the step of reconditioning the polishing pad isperformed synchronously with the step of polishing the wafer. In someembodiments, the step of reconditioning the polishing pad is performedagain after the step of polishing the wafer.

In accordance with alternative embodiments of the present disclosure, achemical mechanical polishing system includes a chemical mechanicalpolishing apparatus and a controller. The chemical mechanical polishingapparatus includes a polishing pad, a sensor, a polishing head and aconditioner. The sensor is configured to obtain surface roughness of thepolishing pad. The polishing head is located above the polishing pad andconfigured to polish a wafer which is push against the polishing pad.The conditioner is located on the polishing pad and configured torecondition the polishing pad. The controller is coupled to the chemicalmechanical polishing apparatus, and is configured to tune at least onepolishing condition according to the surface roughness of the polishingpad and control the conditioner according to the at least one polishingcondition. In some embodiments, the sensor is configured to captureimages of the polishing pad to obtain surface roughness of the polishingpad. In some embodiments, the sensor includes confocal microscopy or athree-dimensional image sensor.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A chemical mechanical polishing apparatus, comprising: a polishingpad; a sensor configured to obtain surface roughness of the polishingpad; a polishing head located above the polishing pad and configured topolish a wafer which is push against the polishing pad; and aconditioner located on the polishing pad and configured to reconditionthe polishing pad, wherein the conditioner is operated according to atleast one polishing condition, and the polishing condition is tunedaccording to the surface roughness of the polishing pad.
 2. The chemicalmechanical polishing apparatus according to claim 1, wherein the sensoris configured to capture images of the polishing pad to obtain surfaceroughness of the polishing pad.
 3. The chemical mechanical polishingapparatus according to claim 2, wherein the sensor comprises confocalmicroscopy or a three-dimensional image sensor.
 4. The chemicalmechanical polishing apparatus according to claim 1, wherein a field ofview of the sensor is smaller than an area of the polishing pad, andwherein the chemical mechanical polishing apparatus further comprises: arobotic arm configured to move the sensor between a center and an edgeof the polishing pad so that the sensor is able to capture imagescorrespond to regions between the center and the edge of the polishingpad.
 5. The chemical mechanical polishing apparatus according to claim4, wherein the robotic arm is further configured to move the conditionerbetween the center and the edge of the polishing pad so that theconditioner is able to polish the polishing pad from the center to theedge of the polishing pad.
 6. The chemical mechanical polishingapparatus according to claim 1, wherein the at least one polishingcondition comprises at least one of a rotational speed of theconditioner, a downward force of the conditioner that pushes the waferagainst the polishing pad and a polishing time of the conditioner.
 7. Acontrol method for chemical mechanical polishing apparatus having apolishing pad, a sensor, a polishing head and a conditioner, the controlmethod comprising: capturing, by the sensor, images of the polishing padto obtain surface roughness of the polishing pad; tuning at least onepolishing condition according to the surface roughness of the polishingpad; polishing a wafer which is push against the polishing pad by thepolishing head; and reconditioning, by the conditioner, the polishingpad according to the at least one polishing condition.
 8. The controlmethod according to claim 7, wherein the sensor comprises confocalmicroscopy or a three-dimensional image sensor.
 9. The control methodaccording to claim 7, wherein a field of view of the sensor is smallerthan an area of the polishing pad, and wherein capturing the images ofthe polishing pad comprises: moving the sensor between a center and anedge of the polishing pad so that the sensor is able to capture imagescorrespond to regions between the center and the edge of the polishingpad.
 10. The control method according to claim 9, wherein reconditioningthe polishing pad comprises: moving the conditioner between the centerand the edge of the polishing pad so that the conditioner is able topolish the polishing pad from the center to the edge of the polishingpad.
 11. The control method according to claim 10, wherein the sensorand the conditioner are moved synchronously.
 12. The control methodaccording to claim 7, wherein the at least one polishing conditioncomprises at least one of a rotational speed of the conditioner, adownward force of the conditioner that pushes the wafer against thepolishing pad and a polishing time of the conditioner.
 13. The controlmethod according to claim 7, wherein the step of reconditioning thepolishing pad is performed prior to the step of polishing the wafer. 14.The control method according to claim 13, wherein the step ofreconditioning the polishing pad is performed again after the step ofpolishing the wafer.
 15. The control method according to claim 14,wherein the step of reconditioning the polishing pad is performed againsynchronously with the step of polishing the wafer.
 16. The controlmethod according to claim 15, wherein the step of reconditioning thepolishing pad is performed for the third time after the step ofpolishing the wafer.
 17. The control method according to claim 7,wherein the step of reconditioning the polishing pad is performedsynchronously with the step of polishing the wafer.
 18. The controlmethod according to claim 17, wherein the step of reconditioning thepolishing pad is performed again after the step of polishing the wafer.19. A chemical mechanical polishing system, comprising: a chemicalmechanical polishing apparatus, comprising: a polishing pad; a sensorconfigured to obtain surface roughness of the polishing pad; a polishinghead located above the polishing pad and configured to polish a waferwhich is push against the polishing pad; and a conditioner located onthe polishing pad and configured to recondition the polishing pad; and acontroller coupled to the chemical mechanical polishing apparatus, andis configured to tune at least one polishing condition according to thesurface roughness of the polishing pad and control the conditioneraccording to the at least one polishing condition.
 20. The chemicalmechanical polishing system according to claim 19, wherein the sensorcomprises confocal microscopy or a three-dimensional image sensor.